Effect of interface on the thermal conductivity of thermal barrier coatings: A numerical simulation study

Interface is an important structure in the materials, some rather peculiar physical phenomena can occur at the interface under the application of the exterior physical field. Especially, the grain boundary, phase interface and layer interface are significant factors for improving the thermal insulation behavior of thermal barrier coatings (TBCs). In this paper, finite element method was employed to simulate the heat transfer behavior of TBCs with different interfacial characteristic based on several different interfacial thermal resistance (ITR) models. The simulation results indicate that the heat flux around the interface has exhibited fantastic changing characteristic, the thermal insulation effect of TBCs would be enhanced with the area of the interface increasing. The interface roughness (amplitude) also has a very important effect on the effective thermal conductivity of the as-sprayed TBCs. A novel method, Computational Micromechanics Method (CMM), was utilized to depict the heat transfer behavior of actual coatings with irregular inner interface. The "thermal rectification" mechanism of heat diffusion around the interface make that the heat flux which passes through the interface has exhibited different flow characteristic compared with the positions without interface. In addition, some simple experiments have further verified the existence of the ITR between the bond-coat and top-coat. The investigation results will also provide us a powerful guide to design coating with high thermal insulation property using the physical theory and mechanism of the ITR.